Valves are devices that regulate, direct, and/or control the flow of a fluid (e.g., gases, liquids, fluidized solids, slurries, etc.) by opening, closing, or partially obstructing various passageways. Valves are often categorized based on the mechanism used to control fluid flow (e.g., ball valves, butterfly valves, choke valves, piston valves, plug valves, poppet valves, etc.).
Ball valves are a type of valve that typically include a spherical disc or valve member carried within a valve body. The spherical valve member includes a passage that can be selectively aligned with ports in the valve body by rotating the valve member relative to the valve body. When the passage aligns with one port and any number of the remaining ports, the valve is said to be in the open position. When the passage is out of alignment with the ports, the valve is said to be in the closed position. Ball valves are categorized as “quarter-turn” valves because a ninety degree rotation of the valve member (i.e., a quarter turn) is typically used to transition the valve between the open position and the closed position.
Ball valves can be classified based on the number of connections formed by the valve (e.g., two-way valves, three-way valves, etc.), the shape of the passage through the spherical valve member (e.g., L-shaped, T-shaped, X-shaped, etc.), and the size of the passage through the valve member (e.g., full bore, reduced bore, etc.). Three-way ball valves are often used to switch between two separate fluid supplies and/or returns.
Conventional three-way ball valves do not transition between supplies and/or returns without mixing. In a conventional three-way ball valve, rotating the valve member typically causes the flow rate of one fluid supply to be incrementally increased while the flow rate of another fluid supply is incrementally decreased. When the valve member is halfway rotated, the resulting fluid output is generally a mixture of the two fluid supplies.